Process of smelting iron ores and producing ferrochromium.



No. 790.893. 7 PATENTED MAY 23, 1905.

. z B. P. PRICE. PROCESS OF SMELTING IRON ORES AND PRODUCINGFERROGHROMIUM.

APPLIOATION FILED OOT. 19.1904.

$5 v I Ina/611x30 5:" I wux wtmt Jtt ys,

UNITED STATES 'ratentea Liay 23, 1905.

PATENT OFFICE.

PROCESS OF SMELTING IRON ORES AND PRODUCING FERROCHROMIUM.

SPECIFICATION forming part of Letters Patent N0. 790,393, dated May 23,1905. Application filed October 19, 1904. Serial No. 229,167.

To all whom. zit/may concern:

Be it known that I, EDGAR F. PRICE, a citizen of the United States.residing at Niagara Falls, in the county of Niagara and State ofNewYork, have invented certain new and useful Improvements in Processesof Smelting Iron Ores and Producing Ferrochromium, of

which the following is a specification.

In the production of ferrochromium from chromite it is customary tointroduce a small charge of the ore, carbon, and a flux into an.

, ore is reduced a layer of the ferrochromium through the metaltap-hole.

accumulates on the hearth, covered by a layer of slag. The molten alloyis tapped out from time to time until the slag has increased to such anamount as to require removal. As the normal slag has a highfusion-point, a flux is added to render it more liquid, and theremaining alloy and slag are finally run out w The furnace is thencharged anew and the process is repeated. It is important that theferrochromium produced should below in carbon. The amount of carbon inthe charge is therefore kept at a minimum. On account of the lowpercentage of admixed carbon, however, highly-oxidizing gases areevolved in contact with the depending electrode,which is soon consumedand must be replaced. The air also acts rapidly on the hot electrodewhen the furnace is emptied by the removal of slag. Since the charge isa fairly good conductor of electricity, a thin layer only is maintainedaround the lower end of the depending electrode to prevent excessiveshunting of current to the carbon sides of the furnace under the highapplied potential. Much heat is therefore lost by radiation from thezone of reduction through the charge, while the electrode isinsufficiently protected from oxidation by the air. This loss of heatgreatly decreases the reduction efficiency of the furnace Furthermore,the slag is not kept at a sufficiently high temperature to permit it tobe tapped out except by adding'large amounts of flux, discontinuing thecharging of ore, and employing the energy of the are merely to liquefythe slag. The heat losses are also increased by the discontinuous modeof working, both the furnace and the depending electrode cooling downwhen the furnace is emptied.

.According to. the present invention the reduction of chromite,magnetite, and other ores of iron is effected in anincandescence-furnace by a continuous operation, the charge and itsproducts being employed as a resistance-conductor. The construction ofthe furnace and the arrangement of the terminal electrodes is preferablysuch that the density of the current increases through the charge fromthe point where it is introduced into the furnace to the point ofreduction,'thereby gradually raising the temperature of the charge. Theterminal electrodes are preferably of iron and they are maintained at arelatively low temperature by the use of a cooling medium. The preferredfurnace is a downwardly-converging vertical stack, one of the electrodesbeing a waterjacketed horizontal iron ring at the upper end of thefurnace and the lower electrode comprising a water-cooled horizontaliron plate, constituting the hearth of the furnace, and a body of theiron or alloy produced by the reduction of the ore and supported by thehearthplate, this body being in a molten condition except at its lowerend,where it is maintained in a pasty or solid condition by the coolingaction of water circulated through the hearth. Iron or an iron alloycontaining a minimum or definite percentage of carbon may be produced byemploying a charge containing a predetermined amount of carbon.

A suitable electric furnace is shown in the accompanying drawing, inwhichthe figure is a vertical axial section.

The furnace is a vertical stack comprising a downwardly-converging body1 of refractory non-conductive material, such as magnesia or siloxiconfire-brick, surrounded by a waterjacket 2. The body is supported upon ahorizontal metal plate 3, preferably of cast-steel, having a chamber 4:for the circulation of water and an electric terminal 5. A body 13 of amolten metal or alloy is supported on the plate 3, this body and plateconstituting the lower electrode of the furnace. Supported upon the body1, but insulated therefrom by a layer 6 of refractory non-conductivematerial, is the upper electrode 7, a downwardlyconvergingwater-jacketed iron ring having a terminal 8, the inner surface of thering being bare, so that it may contact with the charge. Supported uponthe electrode-ring is an iron ring 9, which carries a bell-andhoppercharging mechanism 10. An outletflue 11 for waste gases extends from thering 9. A tap-hole 12 for the molten product extends laterally throughthe body 1 at some distance above the hearth-electrode. In employingthis furnace to carry out the process acharge which is electricallyconductive or which will be converted into a conductor by thetemperature of the furnaoefor example, a mixture of chromite, coke,lime, and silica-is fed into the furnace until it substantially fillsthe stack, the upper portion of the charge lying in contact with thering-electrode 7. If the charge is normally a poor conductor,initial-current paths between the electrodes are provided. Theconductivity of the charge may be increased by using a mixturecontaining large pieces of coke, which lie in contact with each other atvarious points, and thereby afford direct paths for the flow of current.An electric current is then passed from the upper electrode through thecharge to the hearth, the charge serving as a resistance-conductor, inwhich the temperature gradually rises toward the hearth by reason of thedecreasing cross-section and increasing current density to a point wherereduction is effected. The reduced iron and chromium form a moltenalloy, which accumulates in a body 13 in the lower part of the stackbelow the taphole 12, this body being molten except for a layer 14 inproximity to the hearth, which is maintained in a pasty or solidcondition by water circulated through the chamber 4. of the hearth.During the normal operation of the furnace the body 18 serves as thelower electrode, the hearth 3 then constituting merely a terminalelectrode. Further reduction of the charge causes the accumulated bodyto rise above the level of the tap-hole 12, and the excess is tapped outfrom time to time or continuously, fresh charge material being fed intothe furnace at the top. The process is thus a continuous one. The Wastegases passing up from the zone of reduction through the charge serve topreheat it and are withdrawn through the flue 11 and utilized for fuel.

By employing a charge containing a predetermined amount of carbon it ispossible to produce iron or an iron alloy containing a minimum ordefinite percentage of carbon.

The use of electrodes of iron, and especially of an iron electrode incontact with the molten iron reduced from the charge, is a decidedimprovement over the use of electrodes of carbon, which would dissolvein the product and give it a high and variable percentage of carbon.

The claims of this application are specifically directed to thereduction of iron ores, the reduction of refractory ores in general, andspecifically the reduction of calcium compounds for the production ofcalcium carbid, being claimed in my Patent No. 7 82, 922, dated February21, 1905.

I claim 1. The process of smelting ores containing iron, which consistsin interposing a charge of the ore and a reducing agent as aresistanceconductor between metal electrodes, electrically heating saidcharge to the tenmerature requisite for reduction, and cooling theelectrodes to maintain them at a relatively low temperature, as setforth.

2. The process of smelting ores containing iron, which consists ininterposing a charge of the ore and a reducing agent as aresistanceconductor between electrodes, one of said electrodes being ofiron or an iron alloy and comprising a liquid portion and a solidportion, electrically heating said charge to the temperature requisitefor reduction, and cooling the solid portion of said metal electrode, asset forth.

3. The process of smelting ores containing iron, which consists ininterposing a charge of the ore and a reducing agent as aresistanceconductor between superposed electrodes, the lower electrodebeing of iron or an iron alloy and comprising a liquid portion and asolid portion, electrically heating said charge to the temperaturerequisite for reduction, and cooling the solid portion of the lowerelectrode, as set forth.

4:. The process of smelting ores containing iron, which consists ininterposing a charge of the ore and a reducing agent as aresistanceconductor between superposed electrodes, the lower electrodebeing of iron or an iron alloy and comprising a liquid portion and asolid portion, electrically heating said charge to the temperaturerequisite for reduction, cooling the solid portion of the lowerelectrode, permitting the molten product to settle and collect upon thelower electrode, and removing the product and supplying fresh chargematerials as required, as set forth.

5. The process of smelting ores containing iron, which consists ininterposing a charge of the ore and a reducing agent as aresistanceconductor between metal electrodes, electrically heating saidcharge to the temperature requisite for reduction by an electric currentthe density of which increases through the charge, and cooling theelectrodes to maintain them at a relatively low temperature, as setforth.

6. The process of smelting ores containing iron, which consists ininterposing a charge of the ore and a reducing agent as aresistanceconductor between electrodes, one of said electrodes being ofiron or an iron alloy and comprising a liquid portion and a solidportion, electrically heating said charge to the temperature requisitefor reduction by an electric current the density of which increasesthrough the charge, and cooling the solid portion of said metalelectrode, as set forth.

7 The process of smelting ores containing iron, which consists ininterposing a charge of the ore and a reducing agent as aresistanceconductor between superposed electrodes, the lower electrodebeing of iron or an iron alloy and comprising a liquid portion and asolid portion, electrically heating said charge to the temperaturerequisite for reduction by an electric current the density of whichincreases through the charge, cooling the solid portion of the lowerelectrode, permitting the molten product to settle and collect upon thelower electrode, and removing the product and supplying fresh chargematerials as required, as set forth.

8. The process of smelting ores containing iron and an alloying metal,which consists in interposing a charge of the ore and a reducing agentas a resistance-conductor between metal electrodes, electrically heatingsaid charge to the temperature requisite for reduction, and cooling theelectrodes to maintain them at a relatively low temperature, as setforth.

9. The process of smelting ores containing iron and an alloying metaland producing an alloy containing a minimum or definite percentage ofcarbon, which consists in interposing a charge of the ore and apredetermined amount of carbon as a resistance-conductor between metalelectrodes, electrically heating said charge to the temperaturerequisite for reduction, and cooling the electrodes to maintain them ata relatively low temperature, as

' set forth.

10. The process of smelting ores containing iron and an alloying metaland producing an alloy containing a minimum or definite percentage ofcarbon. which consists in interposing a charge of the ore and apredetermined amount of carbon as a resistance-conductor betweenelectrodes, one of said electrodes consisting of the alloy to beproduced and comprising a liquid portion and a solid portion,

ture requisite for reduction, cooling the solid portion of said alloyelectrode, permitting the molten product to settle and collect upon thelower electrode, and removing the product and supplying fresh chargematerials as required, as set forth.

12. The process of smelting ores containing iron and an alloying metaland producing an alloy containing a minimum or definite per .centage ofcarbon, which consists in interposing a charge of the ore and apredetermined amount of carbon as a resistance-conductor between metalelectrodes, electrically heating said charge to the temperaturerequisite for reduction by an electric current the density of whichincreases through the charge, and

cooling the electrodes to maintain them at arelatively low temperature,as set forth.

13. The process of smelting ores containing iron and an alloyingmetaland producing an alloy containing a minimum or definite percentageof carbon, which consists in interposing a charge'of the ore and apredetermined amount of carbon as a resistance-conductor betweensuperposed electrodes, the lower electrode consisting of the alloy to beproduced and comprising a liquid portion and a solid portion,electrically heating said charge to the temperature requisite forreduction by an electric current the density of which increases throughthe charge, cooling the solid portion of said alloy electrode,permitting the molten product to settle and collect upon the lowerelectrode, and removing the product and supplying fresh charge materialsas required, as set forth.

14:. The process of smelting chromite and producing ferrochromium, whichconsists in interposing a charge of the chromite and a reducing agent asa resistance-conductor between metal electrodes, electrically heatingsaid charge to the temperature requisite for reduction, and cooling theelectrodes to maintain them at a relatively low temperature, as setforth.

15. The process of smelting chromite and producing ferrochromiumcontaining a minimum or definite percentage of carbon, which consists ininterposing a charge of the chromite and a predetermined amount ofcarbon as a resistance-conductorbetween metal electrodes, electricallyheating said charge to the temperature requisite for reduction, andcooling the electrodes to maintain them at a relatively low temperature,as set forth.

16. The process of smelting chromite and tion, cooling the solid portionof the lower electrode, permitting the molten product to settle andcollect upon the lower electrode, and removing the prod uctand supplyingfresh charge materials as required, as set forth.

17. The process of smelting chromite and producing ferrochromiumcontaining a minimum or definite percentage of carbon, which consists ininterposin g a charge of the chromite and a predetermined amountofcarbon as a re-- consists in interposing a charge of chromite and apredetermined amount of carbon as a resistance-cond uctor betweensuperposed electrodes, the lower electrode consisting of ferrochromiumand comprising a liquid portion and a solid portion, electricallyheating said charge to the temperature requisite for reduction by anelectric current the density of which increases through the charge,cooling the solid portion of the lower electrode, permitting the moltenproduct to settle and collect upon the lower electrode, and removing theproduct and supplying fresh charge materials as required, as set forth.

In testimony whereof I aflix my signature in presence of two witnesses.

EDGAR F. PR ICE. Witnesses:

- G. E. Cox,

JAMES G. l\[ARSlIALL.

